Hydrologic and Sedimentologic Data Collected During Three Cruises on the Mississippi RIver and Some of Its Tributaries From Minneapolis, Minnesota, to New Orleans, Louisiana, July 1991-May 1992

Bed sediments, water, and suspended-sediment samples were collected and water discharge was measured at 12 sites on the Mississippi River. These sites and 14 sites on tributaries to the Mississippi River were sampled on three cruises during an 11-month period from July 5,1991, to May 10,1992. Discharge-weighted pumping and depth-integration methods were used at several equally spaced locations across the river to collect composite samples of river water containing suspended sediment. Water discharge was measured by the depth-integration method and ranged from about 220 cubic meters per second for Mississippi River above St. Anthony Falls, Minnesota, in October 1991 to 21,700 cubic meters per second below Vicksburg, Mississippi, in May 1992. Concentration of suspended sediment in the Mississippi River varied from 9 milligrams per liter downstream from Lake Pepin to 701 milligrams per liter at Thebes, Illinois. This report contains the following hydrologic data associated with the samples: cross sectional area of the river, water depths, depth-averaged velocities, water discharge, and temperature, pH, and specific conductance of the surface water. It contains the following sedimentologic data: concentrations of the suspended sand fraction, silt and clay fraction, and colloid fraction, and particle sizes of bed sediment and suspended sediment. These data provide the framework for interpreting subsequent chemical analyses of the water and suspended-sediment samples collected during the three cruises and for calculating bed-load transport in the Mississipp*' River and some of its tributaries.